Combine 1 cup lemon juice with sugar, raspberries, and salt in a high-powered blender. Blend until completely smooth, about 60 seconds.
Place a fine mesh sieve over a wide-mouth pitcher or wide bowl with a spout. Pour blended mixture through, pressing to extract all you can. I like to chill this mixture for an hour (if time permits).
Pour strained raspberry mixture into a pitcher, then add cold water, gradually, until lemonade is to your liking. I start with 4 cups and taste, then adjust from there. (I like it best with about 5 cups, depending on sweetness of berries). Keep in mind, ice will water it down as well. Pour over ice and enjoy!
Notes
Storage: Store your raspberry lemonade in a pitcher or bottle (in the fridge) without ice for up to 4 days.